With 160 million inhabitants, Nigeria is the most populous African nation, and home to the second largest number of people living with HIV/AIDS in the world (3.5 million). In Nigeria and other resource-limited countries (RLS), loss to follow-u (LTFU) poses a major challenge to the successful provision of chronic HIV care. One in four patients are lost-to-follow-up one year after initiating antiretroviral therapy (ART), resulting in loss of over half of the life expectancy gains provided by ART. While some patients are completely lost from HIV care, a lesser-studied group, approximately one in three, briefly interrupt but return to care. Our previous work in South Africa suggests that unplanned care interruptions portend poor patient outcomes. Many studies have characterized patient-level predictors of LTFU, but this knowledge has not enabled service providers to adequately improve patient retention. In addition, few studies have systematically assessed whether health system-level characteristics, which vary widely across treatment programs, predict LTFU and unplanned care interruption. Missing from the assessment of both patient and health system-level predictors of LTFU is an assessment of how these factors inform patient decisions to remain in HIV care, a concept known as decisional conflict. My goal in this proposed K23 award is to utilize a novel framework incorporating health system and patient-level predictors of LTFU and unplanned care interruption, with determinants of patient decisional conflict. This will inform development of a pilot intervention to improve patient retention in HIV care in Nigeria. To accomplish this goal, I will study the AIDS Prevention Initiative Nigeria's (APIN) network in 32 comprehensive HIV treatment centers in 9 of Nigeria's 36 states. I will first investigate health system factors predictive of LTFU and unplanned care interruption by surveying clinic directors on a range of health system services available to their patients, and assessing outcomes of 1,500 patients over one year. I will then establish a cohort of 752 ART-eligible adults to determine the relationship of patient risk factors related to decisional conflict (disease severity stigma, resource deprivation and competing needs) about adhering to chronic HIV care, and the association between decisional conflict and both LTFU and unplanned care interruption one year after ART initiation. Finally, I will build on these findings to develop a pilot intervention n HIV-infected, ART-eligible patients based on a home-based HIV care construct to ameliorate decisional conflict by addressing both health system processes and patient obstacles to HIV care. The research proposed in this K23 award will build on my previous training in epidemiology and biostatistics, allow me to receive further training in quality improvement theory and methodology as well as technical expertise in large program evaluation and intervention design, and will ideally position me to launch my career as an investigator in HIV outcomes and implementation science in RLS.